We plan to use this adoption sample in which significant genetic, environmental, and gene-environment factors for drug abuse vulnerability have been found in an association study using candidate genes which have been implicated in substance abuse. We predict that the inclusion in the association analysis of information available through the adoption paradigm about environmental and gene-environment interaction effects will increase the efficiency of detecting gene-behavior associations. Specific goals for this proposed continuation include: 1. Conducting a 4-year follow-up of the adoptee sample of 95 male and 102 female subjects to achieve better ascertainment of drug abuse in the sample and to evaluate better the effects of other likely genetic sources of drug abuse vulnerability such as biologic parent drug abuse. 2. Collect blood samples from adoptees, extract DNA and use to determine candidate gene association with drug abuse/dependency and other genetically determined behaviors which increase drug abuse vulnerability such as conduct disorder. 3. Efficiency of regression models which include environmental factors to detect association will be tested. This study could lead the way to the use of large pools of adoptees to detect association more effectively since environmental and gene- environment factors can be included in the analysis.